A system and method for operating an internal combustion engine using positive crankcase ventilation (PCV) is described in U.S. Pat. No. 6,729,316. The patent describes a system wherein emissions are pumped from a crankcase to a canister. The canister contains a deceleration and condensing element comprised of glass beads. It is believed that the glass beads decelerate flow originating from the crankcase and cause hydrocarbons to condense so that they can be discharged to a collector. The canister purportedly separates contaminants from the crankcase and then passes the cleansed emissions back to the engine for combustion.
The above-mentioned system can also have several disadvantages. Specifically, fuel vapors are sent to the engine shortly after being processed through the canister. If the crankcase gases are related to a single boiling point fuel (e.g., alcohol), much of the alcohol can transition to the vapor state in a short period of time. As such, concentrated vapors can be drawn into the separating canister and then transferred to the engine at a rate that causes the engine to run rich. Thus, the canister may extract contaminants from the crankcase emissions, but the device does not appear to offer any means to control the rate that exhaust gases are transferred to the engine. Further, if crankcase gases cause the engine to operate rich, the engine controller adaptive fuel strategy may cause the engine to operate lean after the crankcase gases are purged from the engine. Thus, it does not appear that the system improves engine air-fuel control when gasses are purged from the engine crankcase.
The inventors herein have recognized the above-mentioned disadvantages and have developed a system and method that offers substantial improvements.